Feedwell for a gravity separation vessel

ABSTRACT

A feedwell for a gravity separation vessel for introducing a feed stream such as oil sand slurry to the gravity separation vessel is provided comprising a walled member having an upper perimeter edge, a lower perimeter edge and a substantially continuous wall extending from the upper perimeter edge to the lower perimeter edge; an inlet for introducing the feed stream into the walled member positioned adjacent the substantially continuous wall; and a bottom floor having an opening and extending generally beneath the lower perimeter edge; whereby a perimeter of the opening is less than a perimeter of the walled member.

This application is a divisional application of U.S. patent applicationSer. No. 12/881,816 filed Sep. 14, 2010, which claims priority to U.S.Provisional Patent Application No. 61/242,265 filed Sep. 14, 2009.

FIELD OF THE INVENTION

The present invention relates to gravity separation vessels, inparticular, those used for separating bitumen from an oil sand/waterslurry and, more particularly, to the introduction of a slurry to agravity separation vessel.

BACKGROUND OF THE INVENTION

Bitumen extracted from oil sand, such as oil sand mined in the FortMcMurray region of Alberta, is generally made up of water-wet sandgrains and viscous bitumen. To eventually produce a commercial petroleumproduct from oil sand, the bitumen must be removed from the sand. Toremove the bitumen from the sand/bitumen mixture, the oil sand is oftencrushed and then mixed with water to form an oil sand/water slurry. Thisslurry can then be subjected to what is commonly referred to as“pipeline conditioning” by pumping the slurry some distance through apipeline, commonly called a hydrotransport pipeline. The conditionedslurry is then typically diluted with a fluid, such as water, to form adiluted slurry. By diluting the slurry, the density of the slurry can bealtered to a more desirable density for separation of the bitumen in theslurry. The diluted slurry is then fed to a gravity separation vesselsuch as a primary separation vessel (PSV) where the relatively quiescentconditions and entrained air in the bitumen allows a significant portionof the bitumen to float towards the top of the gravity separation vesseland collect in a layer of froth, commonly called primary bitumen froth.This primary bitumen froth can be recovered and further treated toeventually be made into a commercial petroleum product.

In addition to the bitumen froth layer, typically a middlings layer anda tailings layer are also formed in the gravity separation vessel. Themiddlings layer forms below the bitumen froth layer and the tailingslayer forms at the bottom of the gravity separation vessel. Themiddlings and tailings layers are removed and often further treated toextract out additional bitumen that remains in these layers. However,the bitumen in these layers is not as easily recoverable.

To try and increase the quality of the bitumen froth that collects inthe bitumen froth layer, an underwash layer is often purposely formedabove the middlings layer and below the bitumen froth layer in the PSV.The underwash layer is typically formed by introducing heated liquid,such as water, to the upper portion of the middlings layer and below thebitumen froth layer. The heated liquid in the underwash layer can helpto increase the temperature of the bitumen froth produced. The heatedunderwash water can also replace the middlings in the bitumen froth asit is formed, thereby reducing the amount of solids in the froth.

To enhance gravity separation, quiescent conditions need to bemaintained in the PSV. One of the main factors affecting these quiescentconditions is the introduction of the slurry to the gravity separationvessel. Typically, these gravity separation vessels are operated as acontinuous process with slurry continuously being introduced into thegravity separation while end products, such as bitumen froth, a tailingsstream, etc. are continuously being removed from the gravity separationvessel. The introduction of slurry can have a detrimental effect onthese quiescent conditions due to the high velocity of the feed and therecirculation currents formed by the separation of the coarse solidsfrom the slurry. Additionally, the introduction of the slurry can have adetrimental effect on the underwash layer, with swirling and vorticescreated in the gravity separation vessel by the introduction of theslurry affecting the stability of the underwash layer and causing anerosion of the underwash layer.

SUMMARY OF THE INVENTION

In a first aspect, a feedwell for use in a gravity separation vesselwhich provides more uniform distribution in the vessel as the influentstream enters the vessel for separation is provided. The feedwellcomprises: a walled member having an upper perimeter edge, a lowerperimeter edge and a substantially continuous wall extending from theupper perimeter edge to the lower perimeter edge; an inlet forintroducing a feed stream such as oil sand slurry into the walled memberpositioned adjacent the substantially continuous wall; and a bottomfloor having an opening and extending generally beneath the lowerperimeter edge; whereby a perimeter of the opening is less than aperimeter of the walled member. In one embodiment, the feedwell furthercomprising a deflector plate having a generally conical shape andspacedly position beneath the opening of the bottom floor.

In one embodiment, the substantially continuous wall defines asubstantially cylindrical space and the opening in the bottom floor ispositioned substantially centrally and is substantially circular inshape having a diameter that is smaller than the inner diameter of thewalled member. Thus, the feed stream level in the walled member willincrease, providing a pool in the chamber into which the kinetic energyfrom the inlet feed stream flow can be dissipated. Hence, the opening inthe bottom floor is sized to maintain the liquid pool level in thecylindrical space of the feedwell.

In another embodiment, the feedwell further comprises an extension pipeattached to the opening to divert the flow of the feed stream from theopening directly onto the center or apex of the conical deflector plate.The extension pipe favors an axisymmetric down-flow which impacts ontothe apex producing a circumferentially uniform discharge. It isunderstood that the opening must be of a sufficient size to allow thepassage of the entire feed stream, including any lumps that may bepresent therein.

In another embodiment, the feedwell further comprises at least onesubstantially vertical baffle located within the walled member forreducing the momentum of the feed stream as it enters the walled member.In one embodiment, the width of the baffles may increase in the rotationdirection as you move away from the inlet with the thinnest baffleposition directly in line with the feed stream inlet, thus, preventingexcessive erosion of the baffles located closest to the feed inletpoint. It is understood that baffles can be different shapes as known inthe art, for example, L shaped baffles can be used.

In another aspect, a feedwell for a gravity separation tank forintroducing a slurry to the gravity separation vessel is provided. Thefeedwell comprises: a walled member having an upper perimeter edge, alower perimeter edge and a substantially continuous wall extending fromthe upper perimeter edge to the lower perimeter edge; an inlet forintroducing a feed stream into the walled member positioned adjacent thesubstantially continuous wall; a bottom plate having a first openingextending generally beneath the lower perimeter edge; a first deflectorplate having a second opening and a generally frusto-conical shape andpositioned beneath the first opening such that the feed is directed fromthe first opening to the second opening of the first deflector plate;and a second deflector plate having a generally conical shape andspacedly positioned below the first deflector plate so that when thefeed goes through the second opening it is distributed between the twodeflector plates.

It is understood that the space between the first and second deflectorplates should be sufficient to allow any large lumps in the feed streamto pass therebetween. For example, when the feed is oil sand slurry, itis possible to have lumps therein having a diameter of about 2 to 4inches. In one embodiment, the first and second deflector plates aresubstantially parallel. However, it is understood that the plates can beeither convergent or divergent, provided, however, that the narrowestspace between the plates is sufficient to allow the passage of thelargest lumps in the feed stream therebetween.

In another aspect, a gravity separation vessel is provided. The gravityseparation vessel has a separation chamber for holding slurry to beseparated, an underwash pipe for supplying heated liquid to theseparation chamber, the underwash pipe extending into the separationchamber, at least one underwash outlet connected to the underwash pipeat a predetermined height in the separation chamber and operative toroute heated liquid from the underwash pipe to the separation chamberand a feedwell for supplying slurry to the gravity separation vessel.The feedwell has a walled member having an upper perimeter edge, a lowerperimeter edge and a substantially continuous wall extending from theupper perimeter edge to the lower perimeter edge; an inlet forintroducing a feed stream into the walled member adjacent thesubstantially continuous wall; a bottom plate having an openingextending generally beneath the lower perimeter edge; and a deflectorplate having a generally conical shape and spacedly positioned beneaththe central opening of the bottom plate. The feedwell is positioned sothat the outer periphery of the deflector plate is positioned below theunderwash outlet(s).

In another aspect, a gravity separation vessel is provided. The gravityseparation vessel has a separation chamber for holding slurry to beseparated, an underwash pipe for supplying heated liquid to theseparation chamber, the underwash pipe extending into the separationchamber, at least one underwash outlet connected to the underwash pipeat a predetermined height in the separation chamber and operative toroute heated liquid from the underwash pipe to the separation chamberand a feedwell for supplying slurry to the gravity separation vessel.The feedwell has a walled member having an upper perimeter edge, a lowerperimeter edge and a substantially continuous wall extending from theupper perimeter edge to the lower perimeter edge; an inlet forintroducing a feed stream into the walled member adjacent thesubstantially continuous wall; a bottom plate having a central openingextending generally beneath the lower perimeter edge; a first deflectorplate having a generally frusto-conical shape and positioned beneath thecentral opening such that the feed is directed through the opening ofthe first deflector plate; and a second deflector plate having agenerally conical shape and spacedly positioned below the firstdeflector plate so that the feed is distributed between the twodeflector. The feedwell is positioned so that the outer periphery of thelower deflector plate is positioned below the underwash outlet(s).

In another aspect, a method for introducing a slurry comprising oil sandand water to a gravity separation vessel is provided. The methodcomprises: providing the slurry to a feedwell; passing the slurry thougha chamber of the feedwell; and discharging the slurry from the chamberof the feedwell through a deflector assembly by first routing the slurrydownwards and outwards through the deflector assembly and then routingthe slurry substantially horizontally outwards from the deflectorassembly into the gravity separation vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings wherein like reference numerals indicatesimilar parts throughout the several views, several aspects of thepresent invention are illustrated by way of example, and not by way oflimitation, in detail in the following figures. It is understood thatthe drawings provided herein are for illustration purposes only and arenot necessarily drawn to scale.

FIG. 1 is a schematic side illustration of a gravity separation vessel;

FIG. 2 is a side view of a feedwell for introducing slurry to a gravityseparation vessel;

FIG. 3 is a sectional top view of the feedwell of FIG. 2 along line AA′;and

FIG. 4 is a schematic side sectional view of the feedwell of FIG. 2;

FIG. 5 is schematic side illustration of a gravity separation vessel inanother aspect;

FIG. 6 is a side view of a feedwell used in the gravity separationvessel shown in FIG. 5;

FIG. 7 is a sectional top view of the feedwell of FIG. 6 along line BB′;and

FIG. 8 is a schematic side sectional view of the feedwell of FIG. 6.

DESCRIPTION OF VARIOUS EMBODIMENTS

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various embodiments of thepresent invention and is not intended to represent the only embodimentscontemplated by the inventor. The detailed description includes specificdetails for the purpose of providing a comprehensive understanding ofthe present invention. However, it will be apparent to those skilled inthe art that the present invention may be practiced without thesespecific details.

FIG. 1 illustrates a gravity separation vessel 10 such as a primaryseparation vessel (PSV) for use in extracting bitumen from an oilsand/water slurry. Diluted oil sand/water slurry (which has typicallybeen conditioned by hydrotransport through pipelines) is introduced intothe gravity separation vessel 10 and, under quiescent conditions, thebitumen froth separates from the water and solids. Typically, thegravity separation vessel 10 is operated as a continuous process so thatdiluted slurry is continuously being introduced into the gravityseparation vessel 10 while end products, such as bitumen froth, atailings stream, etc. are also being continuously removed.

The gravity separation vessel 10 has a separation chamber 12. Typically,the separation chamber 12 will have a generally cylindrical upperportion 14 and a generally conical bottom portion 16. The upper portion14 can have an open top and a feedwell 50 provided in the upper portionthrough which the diluted slurry enters the gravity separation vessel 10at the upper portion 14 of the separation chamber 12.

The diluted slurry, once introduced into the separation chamber 12,forms a number of layers in the separation chamber 12; including abitumen froth layer 22 at the top of the separation chamber 12, amiddlings layer 24 below the bitumen froth layer 22 and a tailings layer26 at a bottom of the separation chamber 12.

Typically, the froth layer 22 contains a significant portion of bitumenand lesser portions of water and solids mixed together in an aircontaining froth. The specific amount of bitumen, water and solids willdepend on the quality of the mined oil sand, such as its bitumencontent, fines content, etc and the process conditions. The froth layer22 is formed by the quiescent conditions in the gravity separationvessel 10 where the aerated bitumen floats to the surface of the liquidin the gravity separation vessel 10, forming the froth layer 22. Themiddlings layer 24 is typically in a liquid/watery form and containsbitumen, water and suspended solids and is positioned below the frothlayer 22 in the gravity separation vessel 10. The tailings layer 26 islocated at the bottom of the gravity separation vessel 10 and typicallycontains a majority of sand which has settled out of the liquid in thegravity separation vessel 10 and has sunk towards the bottom of thegravity separation vessel 10.

The froth layer 22 in the gravity separation vessel 10 can be recoveredand routed for further treatment, such as de-aeration, addition of adiluent to form diluted bitumen, etc., so that the recovered bitumen canbe further upgraded to a petroleum product. In one aspect, the frothlayer 22 can be recovered by allowing it to overflow a top lip 34 of thegravity separation vessel 10 whereby this overflow of bitumen froth canbe collected in a launder 30 and conveyed away for further treatment.

The middlings layer 24 can also be removed from the gravity separationvessel 10, such as by pipe 36, and further treated to recover at leastsome of the bitumen that has remained in the middlings layer 24.

The tailings layer 26 containing sand and other solids that have settledout of the liquid in the gravity separation vessel 10 can be removedfrom the gravity separation vessel 10 as a tailings stream, such asthrough a bottom outlet 32. The tailings stream can either be discardedor further treated to remove additional bitumen that may be present inthe tailings stream.

An underwash layer 28 can be formed at the interface of the middlingslayer 24 and bitumen froth layer 22. The underwash layer 28 can beformed by introducing heated liquid, such as water, into the middlingslayer 24, such as by use of a froth underwash pipe 42 extending downinto separation chamber 12 and having outlets 44 for injecting theheated liquid in the separation chamber 12 to form the underwash layer28 above the middlings layer 24. It is preferred that the underwashlayer be preserved, i.e., remain essentially unperturbed, and some ofthe feedwell embodiments of the present invention have been designed sothat there less interference with the underwash layer.

FIGS. 2 through 4 illustrate the feedwell 50. The feedwell 50 compriseswalled member 52 having an upper perimeter 53, a lower perimeter 55 anda substantially continuous wall 57 with an inlet 62 provided on an upperportion of the walled member 52. The inlet 62 is provided so that it isoriented tangentially to the continuous wall 57 causing the slurry thatis introduced into the feedwell 50 to be introduced into the walledmember 52 of the feedwell 50 in a direction substantially tangential tothe continuous wall 57.

Bottom floor 66 of the walled member 52 of the feedwell 50 has anopening 64 which can have an extension pipe 68 extending therefrom. Theopening 64 can be positioned in the center of the bottom plate 66 of thewalled member 52 and can be sized so that it constrains the amount ofslurry exiting the feedwell 50. In one embodiment, the opening 64 has asubstantially smaller area than the area of the bottom floor 66. Bysizing the opening 64 based on the flow rate that will be used for theslurry entering the feedwell 50 through the inlet 62, the feedwell 50can be designed so that a desired level of slurry can be maintained inthe feedwell 50. If an extension pipe 68 is provided, the extension pipe68 can help to cause a uniform axisymmetric down-flow in the slurryexiting the walled member 52 through the opening 64

In one aspect, a number of baffles 80 can be provided in the walledmember 52 of the feedwell 50 to prevent or minimize swirling flowsand/or vortices in the slurry. In one aspect, the baffles 80 can bepositioned so that the baffles are oriented radially from the center ofthe feedwell 50. The baffles 80 can extend from the walls of the walledmember 52 of the feedwell 50 partially towards the center of thefeedwell 50 and the width of the baffles may increase in the rotationdirection as you move away from the inlet with the thinnest baffleposition directly in line with the feed stream inlet, thus, preventingexcessive erosion of the baffles located closest to the feed inletpoint.

A deflector assembly 70 can be provided below the opening 64 in thebottom floor 66. The deflection assembly 70 can have a deflector plate76 positioned spaced below the opening 64 in the bottom floor 66. In oneaspect, the deflector plate 76 can be generally conically-shaped with aapex 77 of the deflector plate 76 positioned spacedly below the opening64 in the bottom plate 66 so that slurry discharged out of the chamber52 of the feedwell 50 is deflected by the apex 77 of the deflector plate76 to follow the downward slant of the deflector plate 76. Asubstantially horizontal periphery portion 78 of the deflector plate 76can extend outwards to attempt to redirect the flow of slurry exitingthe feedwell 50 horizontally. As slurry is discharged downwards out ofthe opening 64 in the bottom floor 66 towards the generallyconically-shaped deflector plate 76, the deflector plate 76 can redirectat least some of the flow of slurry downwards and outwards along itslength. As the flow of slurry reaches the periphery portion 78, thesubstantially horizontal periphery portion 78 can attempt to direct thisflow substantially horizontally and outwards.

The feedwell 50 may further have a lid 59 at the upper perimeter edge 53having an opening 61, to prevent the slurry feed from splashing outwhile still allowing venting.

Referring to FIGS. 1 through 4, the feedwell 50 is positioned relativeto the separation chamber 12 of the gravity separation vessel 10 suchthat the inlet 62 of the feedwell 50 is positioned above the top of theseparation chamber 12 allowing the slurry to be routed to the inlet 62and thereby into the chamber 52 of the feedwell 50. The chamber 52 ofthe feedwell 50 can extend downwards into the separation chamber 12 sothat the deflection assembly 70 is extending into the middlings layer 24with the outer periphery 78 of the deflector plate 76 positioned in themiddlings layer 24 substantially below the underwash layer 28.

For example, in one aspect the outlets 44 of the froth underwash pipe 42extend approximately 1.5 meters from the top of the separation chamber12 of the gravity separation vessel 10 while the bottom of the extensionpipe 68 on the feedwell 50 extends approximate 2.2 meters below the topof the chamber 12 of the gravity separation vessel 10 and the diluteslurry entering the chamber 12 of the gravity separation vessel 10 as itpasses the deflector plate 76 enters the separation chamber 12 atapproximately 3.5 meters below a top of the separation chamber 12 of thegravity separation vessel 10.

In operation, diluted slurry is introduced into the gravity separationvessel 10 by first introducing the diluted slurry into the inlet 62 ofthe feedwell 50. The tangential orientation of the inlet 62 can cause aswirling/vortex motion in the slurry in the chamber 52 of the feedwell50. If baffles 80 are provided in the walled member 52 of the feedwell50, the baffles 80 can act on the slurry to reduce the swirling of theslurry. As the slurry in the walled member 52 moves towards the bottomplate 66, slurry closer to the center of the walled member 52 of thefeedwell 50 can pass downwards through the opening 64 in the bottomplate 66 of the walled member 52, where less swirling may be present.

As the slurry passes through and out of the walled member 52 of thefeedwell 50, some of the flow of slurry can contact the apex 77 of thedeflector plate 76 and be directed downwards and outwards along thedeflector plate 76. As the slurry exits past the outer periphery 78 ofthe bottom plate 76, at least some of the flow of slurry is directedsubstantially horizontally out into the separation chamber 12 of thegravity separation vessel 10 into the middlings layer 24 and beneath theunderwash layer 28.

FIG. 5 illustrates the separation vessel 10 using a feedwell 150 tointroduce slurry into the separation chamber 12 of the separation vessel10 in a further aspect. FIGS. 6 through 8 illustrate the feedwell 150.The feed well 150 can have a walled member 152 with a tangentiallyoriented inlet 162 provided on an upper portion of the walled member152. An opening 164 can be provided on a bottom floor 166 of the chamber152 of the feedwell 150. The opening 164 can have an extension pipe 179extending downwards therefrom and can be positioned in the center of thebottom floor 166. The opening 164 can be sized so that it constrains theamount of slurry exiting the feedwell 150 to keep a desired level ofslurry in the walled member 152 of the feedwell 150.

In one aspect, a number of baffles 180 can be provided in the walledmember 152 to reduce swirling of slurry in the walled member 152 of thefeedwell 150.

A deflector assembly 170 can be provided below the opening 164 in thebottom floor 166. The deflection assembly 170 can have a first deflectorplate 172 and a second deflector plate 176. In one aspect, the firstdeflector plate 172 has a generally frusto-conical shape and an opening174, which opening 174 is positioned immediately below opening 164 ofthe bottom floor 166. In one embodiment, the opening 174 is connected toopening 164 by an extension pipe 179. The second deflector plate 176 canbe generally conically-shaped with a apex 177 of the deflector plate 176positioned spacedly below the opening 174 of the first deflector plate172 so that slurry discharged out of the walled member 152 flows inbetween the space formed between the two deflector plates 172 and 176.Thus, the feed is deflected by the apex 177 of the second deflectorplate 176 to follow the downward slant of the second deflector plate176. A substantially horizontal periphery portion 178 of the seconddeflector plate 176 can extend outwards to attempt to redirect the flowof slurry exiting the feedwell 150 horizontally. A similar substantiallyhorizontal periphery portion 173 may extend from the first deflectorplate 172.

Thus, the first deflector plate 172 and the second deflector plate 176can act in conjunction to direct at least a substantial portion of theflow of slurry entering the separation chamber 12 from the feedwell 150outwards into the separation chamber 12 in a substantially horizontaldirection beneath the underwash layer 28. The substantially horizontalorientation of the flow of slurry entering the separation chamber 12from the channel 181 formed between the first deflector plate 172 andthe second deflector plate 176 is oriented below the bottom of theunderwash layer 28 to prevent the incoming slurry from eroding the hotliquid forming the underwash layer 28.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to those embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein, but is to beaccorded the full scope consistent with the claims, wherein reference toan element in the singular, such as by use of the article “a” or “an” isnot intended to mean “one and only one” unless specifically so stated,but rather “one or more”. All structural and functional equivalents tothe elements of the various embodiments described throughout thedisclosure that are known or later come to be known to those of ordinaryskill in the art are intended to be encompassed by the elements of theclaims. Moreover, nothing disclosed herein is intended to be dedicatedto the public regardless of whether such disclosure is explicitlyrecited in the claims.

1. A feedwell for a gravity separation vessel for introducing a feedstream such as oil sand slurry to the gravity separation vessel, thefeedwell comprising: a walled member having an upper perimeter edge, alower perimeter edge and a substantially continuous wall extending fromthe upper perimeter edge to the lower perimeter edge; an inlet forintroducing the feed stream into the walled member positioned adjacentthe substantially continuous wall; and a bottom floor having an openingand extending generally beneath the lower perimeter edge; whereby aperimeter of the opening is less than a perimeter of the walled member.2. The feedwell as claimed in claim 1 further comprising a deflectorplate having a generally conical shape and spacedly position beneath theopening of the bottom floor.
 3. The feedwell of claim 1 furthercomprising an extension pipe connected to the opening and extendingdownwardly from the opening to allow for a uniform discharge flow of thefeed stream flows through the extension pipe and onto an upper surfaceof the deflector plate.
 4. The feedwell as claimed in claim 3 furthercomprising a deflector plate having a generally conical shape andspacedly position beneath the extension pipe so that the feed streamflows through the extension pipe and onto an upper surface of thedeflector plate.
 5. The feedwell of claim 2 wherein an apex of thedeflector plate is provided directly below the opening,
 6. The feedwellof claim 2 wherein the deflector plate has a substantially horizontalouter periphery.
 7. The feedwell of claim 1, wherein the opening ispositioned substantially centrally in the bottom floor.
 8. The feedwellof claim 1 further comprising at least one baffle in the walled memberto reduce swirling flows of the feed stream and vortex formation.
 9. Thefeedwell of claim 8, wherein the at least one baffle is arranged aroundthe walled member,
 10. A feedwell for a gravity separation vessel forintroducing a feed stream such as oil sand slurry to the gravityseparation vessel, the feedwell comprising: a walled member having anupper perimeter edge, a lower perimeter edge and a substantiallycontinuous wall extending from the upper perimeter edge to the lowerperimeter edge; an inlet for introducing a feed stream into the walledmember positioned adjacent the substantially continuous wall; a bottomplate having a first opening and extending generally beneath the lowerperimeter edge; a first deflector plate having a generallyfrusto-conical shape and a second opening, the first deflector platepositioned beneath the first opening such that the feed is directed fromthe first opening to the second opening; and a second deflector platehaving a generally conical shape and spacedly positioned below the firstdeflector plate so that when the feed goes through the second opening itis distributed between the two deflector plates.
 11. The feedwell ofclaim 10 wherein the first deflector plate is connected to the firstopening by an extension pipe extending from the second opening.
 12. Thefeedwell of claim 10 wherein the first deflector plate is substantiallyparallel to the second deflector plate.
 13. The feedwell of claim 12wherein the first deflector plate has a substantially horizontalperiphery and the second deflector plate has a substantially horizontalperiphery.
 14. The feedwell of claim 10 further comprising at least onebaffle in the walled member.
 15. The feedwell of claim 10, wherein thefirst opening is positioned substantially centrally in the bottom floor.16. The feedwell of claim 10, wherein the second opening is positionedsubstantially centrally in the first deflector plate.
 17. A gravityseparation vessel comprising: a separation chamber for holding slurry tobe separated; an underwash pipe for supplying heated liquid to theseparation chamber, the underwash pipe extending into the separationchamber; at least one underwash outlet connected to the underwash pipeat a predetermined height in the separation chamber and operative toroute heated liquid from the underwash pipe to the separation chamber; afeedwell for supplying slurry to the gravity separation vessel, thefeedwell comprising: a chamber having a bottom plate; a tangential inletfor accepting liquid into the chamber; a first opening provided in thebottom plate; and a conical deflector plate, the conical deflector platespacedly positioned beneath the first opening, wherein the feedwell ispositioned so that the outer periphery of the conical deflector plate ispositioned below the at least one underwash outlet.
 18. The gravityseparation vessel of claim 17 wherein an apex of the conical deflectorplate of the feedwell is spacedly positioned below the first opening ofthe feedwell.
 19. The gravity separation vessel of claim 17 furthercomprising a frusto-conical deflector plate having a second opening anda substantially horizontal outer periphery, the frusto-conical deflectorplate spacedly positioned above the conical deflector plate andpositioned below the bottom plate, the frusto-conical deflector platespacedly positioned below the at least one underwash outlet.
 20. Thegravity separation vessel of claim 19 wherein the frusto-conicaldeflector plate of the feedwell is substantially parallel to the conicaldeflector plate of the feedwell.
 21. The gravity separation vessel ofclaim 20 wherein the second opening of the frusto-conical deflectorplate of the feedwell is connected to the first opening of the feedwellby an extension pipe.
 22. The gravity separation vessel of claim 17wherein at least one baffle is provided in the chamber of the feedwell.23. The gravity separation vessel of claim 22 wherein the at least onebaffle is an L shaped baffle.
 24. A feedwell for a gravity separationvessel for introducing a feed stream such as oil sand slurry to thegravity separation vessel, the feedwell comprising: a generally planarbottom portion having a first opening; an annular transition portionextending upwardly from the generally planar bottom portion; a sidewallportion extending upwardly from the annular transition portion; atangential inlet for introducing the feed stream into the feedwellabutting the sidewall portion; a first deflector plate having agenerally frusto-conical shape and a second opening, the first deflectorplate positioned beneath the first opening such that the feed isdirected from the first opening through the second opening; a seconddeflector plate having a generally conical shape and spacedly positionedbelow the first deflector plate; and an extension pipe connecting thefirst opening with the second opening so that the feed goes through theextension pipe and is distributed between the two deflector plates. 25.The feedwell of claim 24 wherein the first deflector plate issubstantially parallel to the second deflector plate.
 26. The feedwellof claim 25 wherein the first deflector plate has a substantiallyhorizontal periphery and the second deflector plate has a substantiallyhorizontal periphery.
 27. The feedwell of claim 24 further comprising atleast one baffle in the sidewall portion.
 28. The feedwell of claim 24,wherein the first opening is positioned substantially centrally in thebottom portion.
 29. The feedwell of claim 24, wherein the second openingis positioned substantially centrally in the first deflector plate. 30.A method for introducing a slurry comprising oil sand and water to agravity separation vessel, the method comprising: providing the slurryto a feedwell; passing the slurry though a chamber of the feedwell; anddischarging the slurry from the chamber of the feedwell through adeflector assembly by first routing the slurry downwards and outwardsthrough the deflector assembly and then routing the slurry substantiallyhorizontally outwards from the deflector assembly into the gravityseparation vessel.
 31. The method of claim 30 wherein the slurry isdischarged into the gravity separation vessel below an underwash layerformed with heated liquid.